The couple that Farva says "chicken fucker" to are actually Kevin Heffernan parents. They knew he was going to say something rude, but weren't prepared for the "chicken fucker" line.
In the syrup-chugging scene in the diner, the first few takes were done with the actors drinking thick iced tea from syrup containers, but the iced tea didn't look realistic enough. Real syrup was brought in, and the actors then did several takes in which they actually chugged entire bottles of syrup. These are the takes you see in the close-ups, however, some wide shots with the iced tea were kept in.
The "bullet-proof cup" scene was shot just outside a real-life prison. While Steve Lemme stood there, wearing just a cup, inmates were pressed against the fence yelling at him.
When Rabbit was stuffed in a locker covered in shaving cream, he was actually covered in menthol shaving cream. The crew didn't know that menthol burns skin if left on too long. After the scene, Erik Stolhanske was sent next door to a firehouse to get hosed off.
When Ursula hits Foster in the head with a snowcone, there is a set-up to indicate that the snowcone is solid. A mid-scene switch was supposed to replace the hard snowcone with a softer one, but the switch didn't happen for several takes. Paul Soter took a solid block of ice to the head about nine times before they got it right.